Some help with WPF

Hi all I was wondering if the kind people here can shed some light on WPF. Having searched on the web I seem to be getting more confused about what I am reading. I keep reading about WPF and Silverlight. Are these two completely different languages? Or is
Silverlight a technology and WPF is a programming tool? Can I develop something in expression blend and use it on a mobile device (Windows Phone 7), on the web or as an app?

I am getting Expression Blend this weekend and apparently it is just a tool to design an interface but I am unsure of how to tie in the code with it. Do I export my content from Blend into Visual Studio?

I guess the main question is, if I hear WPF is is referring to Silverlight or am I going to have to learn both.

Sorry for being naive on the subject but the more I read on the matter (from the web) the more I am getting confused by it all. I have seen posts suggesting getting the SAMS Teach Yourself in 24 hours which I have on order :)